The RomProject data format isn't the most reliable format yet. I'm not too surprised that it's breaking like that. It's usually best to work from a clean Rom file every time, though it's not very good if you have a lot of changes to do. Does it export correctly if you load from a Rom instead of a RomProject?

Is the ROM the USA version of Mario Kart? And is it in .z64 format (big endian)? If it isn't both of those, then the program will probably crash when loading. And make sure to click "New Project" instead of "Load Project" when opening a ROM file.

The RomProject data format isn't the most reliable format yet. I'm not too surprised that it's breaking like that. It's usually best to work from a clean Rom file every time, though it's not very good if you have a lot of changes to do. Does it export correctly if you load from a Rom instead of a RomProject?

Update: Making some progress on the course editing. I performed my first rudimentary object manipulation in the editor today, which means I'm just about done with adding new features before I start polishing for a test release.

Of course, by test release I mean something very simple: "You can open courses and view them and move/scale/rotate objects and export it back out to the ROM". There is going to be a LOT of polish needed in order for this to happen, so it'll be some time away in the future still, but these are some basic essentials that after finished will be the foundation for the next step. I'm pretty excited, but I think things will get a bit boring before they get exciting again.

If you send me your modified ROM, I can take a look and see what's different about it that's causing the crash, and then try to fix the issue. It looks like you put a lot of effort into it, so I want to help you finish this up.

If you send me your modified ROM, I can take a look and see what's different about it that's causing the crash, and then try to fix the issue. It looks like you put a lot of effort into it, so I want to help you finish this up.